Not Applicable
Not Applicable
People who own lawns, or are tasked with maintaining them, continually struggle to keep them aesthetically trimmed. The patent record documents many attempts to simplify the task of lawn mowing, but very few innovations have had enough merit to be widely adopted. Today, lawn mowing is still largely a hot, exhausting labor that requires the use of noisy, polluting, dangerous equipment.
The members of a typical yard-owning family would be delighted to wake up each morning and find their grass precisely trimmed to a desired height without any effort on their part, with no related air or noise pollution, with no threat of injury (even to children or pets), with no need to hire mowing personnel who would invade their privacy, and even, with no visible sign of a mower. The present invention can satisfy each of these desires and do so at low cost.
The prior art illustrates a long history of attempts to automate lawn mowing. Almost all of these designs continued the mindset of mowing as a periodic process where a user brings the automatic mower into the area to be mown and returns it to storage after the mowing is completed.
One proposed method of controlling the movement of the mower (U.S. Pat. Nos. 4,347,908, Anderson; 4,831,813, Jones et al.) was to connect it to a physical track that would guide it around the lawn. Another method would use a buried wire for the same purpose (U.S. Pat. Nos. 4,180,964, Pansire; 4,919,224, Shyu et al.). Both approaches are expensive, labor intensive and disruptive to the lawn.
Other designs would require the user to start the mower in exactly the same spot each time and let a storage medium direct the mower to repeat a set of motions made during a recording run. The storage media referenced include magnetic (U.S. Pat. No. 3,789,939, Geislinger), plastic tape (U.S. Pat. Nos. 3,650,097 and 4,354,339, Nokes), or paper tape (U.S. Pat. No. 4,694,639, Chen, et al.). Each of these designs suffers from the amplification of small positional errors. Such errors may be introduced by variations in the mower""s starting location and rotation, by changes in motor efficiency or by wheel slippage caused by such things as variations in grass height, moisture conditions, or temperature.
Noonan, et al., in U.S. Pat. No. 5,204,814, recognized the need to adjust for such variations. He proposed burying metal reference points at various locations along the mower path. The mower would detect these reference points as it passed and use them to correct for any deviations from its desired path. This greatly complicates the initial site preparation and the complexity of the routing algorithm. Instead of just playing back a set of wheel-drive commands recorded by the user, the invention must now know how to interpret sensor data related to the buried metal and override the command playback, The buried markers also make it difficult for the user to modify the mowing geometry after making landscaping changes.
Many of the prior-art patents depend on a pre-defined perimeter only. The perimeter may be a physical barrier, a manually mown strip, or a buried wire. The user must expend considerable effort creating any of these perimeters.
Where there is a manually mown strip, the automatic mower generally uses some form of edge detection to follow the inside edge of the mown strip. It will then spiral inward to the center of the lawn area. The edge detection method could be a mechanical arm with an electrical switch (U.S. Pat. Nos. 3,924,389, Kita; 4,184,559, Rass; 4,887,415, Martin; 5,507,137, Norris), the breaking of a light beam (U.S. Pat. Nos. 4,133,404, Griffin; 4,603,753, Yoshimura; 4,777,785, Rafaels), or a change in motor load (U.S. Pat. Nos. 5,007,234 Shurman, et al.; 5,444,965 Colens). Manufacturers have a hard time making either the mechanical switches or the light beams rugged enough for a mowing environment. They are susceptible to bending and corrosion, clogging with plant debris and juices, and errors caused by changes in moisture content. The systems that search for increased motor loading can be misdirected by non-uniform grass growth rates and moisture content.
Many designs that incorporate a buried perimeter wire (U.S. Pat. Nos. 3,550,714, 3,570,227 and 3,698,523, Bellinger) or a fixed barrier wall (U.S. Pat. No. 5,323,593, Cline, et al.) have used a random mowing pattern. The random-walk approach will significantly extend the time required for all of the grass to be cut.
The concept of using wireless triangulation (U.S. Pat. No. 4,700,301, Dyke) for navigation has been applied to the control of farming equipment. Similarly, satellite navigation using the Global Positionng System [GPS] has been used for utility right-of-way clearing (U.S. Pat. No. 5,666,792, Mullins), rice farming (U.S. Pat. Nos. 5,438,817 and 5,606,850, Nakamura), and the mowing of fields (U.S. Pat. No. 5,528,888, Miyamoto, et al.). For national security reasons, the accuracy of the GPS available to the public was purposefully limited to approximately 100 meters by its administrator, the United States Department of Defense (USDOD). This intentional signal corruption is known as Selective Availability (SA) [see U.S. Pat. Nos. 5,838,562, Gudat, et al., or 5,684,696, Rao, et al., for a detailed description of GPS]. Much of the introduced error can be eliminated using a technique known as differential GPS (DGPS) which compares data from the roving receiver to the same satellite data received at a known fixed location nearby, The most accurate DGPS receiver, however, still has an inherent error of considerably more than one meter and this is not sufficiently accurate for most home, yard, or industrial appliances. The term appliance, as used in this document, is inclusive of mobile machines that perform a wide range of repetitive operations or tasks over a defined work area.
Recently, the traditional concept of mowing as a periodic process has begun to yield to the idea of letting an autonomous mower continually perform the mowing task for the duration of the growing season (U.S. Pat. Nos. 5,323,593, Cline; 5,444,965 Colens). Such an approach has the advantage of further minimizing the amount of user interface required. It also enables the ideal condition of having the lawn always trimmed to the same desired height. Because the incremental amount of grass removed becomes very small, the mower is inherently mulching, so there is no need for the user to be concerned about raking or removing the cut grass. Also, a motor designed to cut off a small increment of grass can be smaller and quieter than a motor designed to wade through tall grass.
Because mowers have traditionally been dangerous appliances, one can see an obvious problem with allowing a mower to continuously mow a lawn. Many toes and fingers have been cut off inadvertently by mower users. Most prudent users would consider it unwise to allow a robotic lawnmower to wander around their lawn continually while their children and pets played in that same yard. At least two inventors have proposed the idea of using thin, razor-blade-like cutting blades that are free to rotate away if they impact something more massive than grass (U.S. Pat. Nos. 4,777,785, Rafaels; 5,444,965 Colens), such as a human hand. While this feature might keep the blade from severing fingers, there is no questioning that a razor blade spinning at thousands of revolutions per minute will do serious damage to an errant hand or foot.
Other automated, or robotic, appliances have gone through an evolution similar to the mowers. Principal among these are floor maintenance appliances which may perform a task such as vacuuming, waxing, or polishing.
As with the mower technology, most of the floor-maintenance prior art approaches the task as a periodic one. The user brings the appliance to the work site and puts it away after the task is complete just as he would if he were performing the work manually. In one instance (U.S. Pat. No. 4,369,543, Chen, et al.), the vacuum is remote controlled by the user.
Many prior art devices have a standard appliance cord that the user must plug into an alternating-current (AC) wall socket (U.S. Pat. No. 5,621,291, Lee). In one example (U.S. Pat. No. 5,634,237, Paranjpe), the user first vacuums a room manually to program the device. The software then figures out how to repeat the process without tangling the cord given the existing set of obstacles. If the objects in the room change, or are moved, the device will need to be reprogrammed. Another device (U.S. Pat. No. 5,841,259, Kim, et al.) uses an ultrasonic sensor to avoid objects and spools out its power cable as it proceeds. It is not clear how it avoids getting the cable tangled up around the objects in the room.
One cleaning device (U.S. Pat. No. 5,537,017, Feiten, et al.), navigates by picking up its cord or a token and moving it a set distance from one side of the machine to the other as it moves from one side of the room to the other. When it reaches the far wall, it turns so that the cord or tokens are on the other side of the device and repeats the procedure in the opposite direction, gradually inching ;its way down the length of the room. While this approach might perform adequately in an open, rectangular room, it would quickly become unworkable in a typically cluttered room.
If users need to configure the device before and after each use, the amount of time saved is likely to be minimal.
Almost all of the prior art uses ultrasonic and or infrared (IR) sensors to help guide the device (U.S. Pat. Nos. 5,001,635, Yasutomi, et al.; 5,440,216, Kim; 5,568,589, Hwang) and detect potential collisions. The typical approach is for the device to traverse the length of a room (U.S. Pat. No. 5,548,511, Bancroft) or hug the perimeter (U.S. Pat. No. 5,867,800, Leif) while gathering sensor input. Using the captured data, the device calculates a path to follow to cover the entire floor surface. The path consists of a sequence of wheel rotations for a desired combination of vehicle translations and rotations. As it follows the dead-reckoned path, the device uses additional sensor data to adjust for implementation errors. This approach may work reasonably well in an open, rectangular room. Most rooms, however, are crowded with different types of furniture or are irregular in shape. Rooms often have a variety of wall coverings as well. Each of these factors changes the magnitude and direction of sonar or IR pulse reflections returning to the machine and complicates navigation. It is also not practical, in most applications, to have a dedicated machine for each room, yet it is very difficult to program these type devices to navigate from room to room.
John Evans, et al., proposed guiding the robot by analyzing images of the overhead light fixtures (U.S. Pat. No. 4,933,864). For institutions that use a standard lighting fixture, this might seem like in appealing approach, but that very regularity would make it difficult to accurately determine where in a given hallway or room the machine is located. Furthermore, the image processing would be complicated by variations in the amount of light reflected from different objects in the room and by burnt-out light bulbs. In a later patent (U.S. Pat. No. 5,051,906), the same inventors proposed adding strips of IR reflective tape to the ceiling. The robot would track its motion by shining an IR source at the ceiling and detecting the pulse of light reflected when the beam crossed the reflective tape. Bruce Field (U.S. Pat. No. 5,020,620) adopted a similar approach with reflective strips placed in front of the appliance. The value of the device to a user will decrease substantially if he needs to start making significant modifications to his environment in order to use the machine. The danger exists that the user may not make the changes correctly or that items will be moved or damaged inadvertently later by the user or by a third party.
John Wilkins (U.S. Pat. No. 4,114,711) proposed using reflective strips to correct the playing back of a recorded sequence of robot motions. This is similar to the approach, described above, of burying metal pieces in a yard to correct the playback of the path recorded for a mower (U.S. Pat. No. 5,204,814, Noonan, et al.). It has the same deficiencies.
Another invention (U.S. Pat. No. 5,165,064, Mattaboni), uses directional IR beacons mounted on the ceiling to help guide the device. Yet another makes use of bar-code scanners (U.S. Pat. No. 5,179,672, Betker, et al.). In each cage the user hag to make and maintain sophisticated modifications to the environment where the appliance will be used.
As with the mowing technology, some cleaning appliances have been designed to move randomly (U.S. Pat. Nos. 4,173,809, Ku; 5,787,545, Colens). The Ku device is simple in design, but cannot recharge itself and is unable to detect stairs or other drop-offs. Since the device follows a random path, it is likely that it would wander from the room where it was started before completing its task there. The machine might then, inadvertently, tumble down a stairway in another room damaging itself and presenting a hazard to the occupants of the building.
The present invention is a multifunctional mobile appliance capable of discerning its position anywhere on or above the surface of the earth to a precision of several millimeters or better using the Real Time Kinematic Global Positioning System (RTK-GPS), or other similar high-precision positioning systems.
By swapping different task performing means, or work modules, onto the front of a mobile unit, the invention can perform a variety of robotic tasks, including, but not limited to, mowing, edging, fertilizing, cultivating, weeding, raking, mulching, vacuuming, sanding, polishing, shampooing, painting, or pressure washing.
In its vegetation-cutting application, the present invention cuts with revolving blades placed inside a mechanical filter structure. The structure allows vegetation to freely pass into the cutting area, but blocks larger objects such as fingers, toes, tree branches, or stones.
The present invention is quiet enough to operate in the middle of the night without disturbing residents. Therefore, it can be programmed to perform a task such as maintaining a lawn at a constant desired height without ever operating while its owner is awake or outside.
The present invention can be battery powered and is capable of recharging itself. After initially guiding the device around the desired operating perimeters, the user need have little involvement with the invention.
The present invention has an obstacle detection system that uses proximity sensors, such as ultrasonic transducers, and impact sensors to help protect the mobile unit and provide it with feedback regarding the job it is performing.
The present invention is small and nimble, allowing it to navigate regions that have narrow stretches or sharp curves that would impede traditional devices. In the illustrated embodiment, the work module extends outside of at least one wheel so that the device can easily perform its task close to walls or over edging strips. For the mowing embodiment, this will eliminate the need for manual edge trimming.
The present invention can communicate with its user through a wireless link that interfaces with the World Wide Web (WWW). In this manner, the invention can send the user email, voice mail, fax or other message formats. Messages might include a printout of a map describing the area over which work is to be performed. Other messages could include status reports or warnings regarding obstacles encountered, such a abandoned toys or fallen tree limbs. The mobile unit could automatically check on-line databases, such as those provided by the weather service, that might help it adapt its use profile to avoid impediments. The invention could periodically download software updates through this same communications link.
The user can easily modify the programmed perimeters that define the areas over which work is to be performed. The same machine can be used to perform a variety of tasks through the simple substitution of interchangeable work modules. The present invention includes appliances that have a single fixed work module as well as those that can substitute different work modules with or without assistance from the user.